Industrial production of useful materials by use of microorganisms is carried out for an extensive range of materials, the types including foodstuffs such as alcoholic beverages, soybean paste and soybean sauce, as well as amino acids, organic acids, nucleic acid-related substances, antibiotic substances, carbohydrates, lipids, proteins, and the like. Applications of these substances are also being expanded over a broad range of fields, including foods, pharmaceuticals, detergents, products for daily use such as cosmetics, and a variety of chemical raw materials.
With regard to such industrial production of useful materials by microorganisms, one important challenge is to improve productivity, and as a measure therefor, breeding of productive microorganisms through genetic techniques such as mutation has been conducted. Recently, in particular, advances in microbial genetics and biotechnology have allowed more efficient breeding of productive microorganisms using genetic recombination technology and the like. In addition, the rapid advancement of genome analysis technology in recent years has resulted in attempts to interpret the genomic data of microorganisms of interest and industrially utilize the obtained information more actively. Examples of industrially useful host microorganisms whose genomic data have been disclosed include Bacillus subtilis Marburg No. 168 (Non-Patent Document 1), Escherichia coli K-12 MG1655 (Non-Patent Document 2), Corynebacterium glutamicum ATCC132032, and the like, and further improved microbial strains have been developed using these genomic data. However, regardless of such efforts, the production efficiencies are not necessarily satisfactory.
For certain types of microorganisms, strains in which a gene associated with the early stage of sporulation has been deleted or inactivated, have been recently constructed, and thereby an effect of improving the productivity for proteins or polypeptides is being obtained. For example, it has been reported that the productivity for the secretion of cellulase and the like is increased by using a host strain in which sigE gene, sigF gene, spoIIE gene, spoIISB gene or sigG gene of Bacillus subtilis, or a group of genes included in a region extending from spoIVCB gene to spoIIIC gene, has been deleted (Patent Document 1).
Furthermore, the functions for operating the protein translocation system (Sec route) in Bacillus subtilis are shared by SecA which serves as a motor for expelling secreted proteins to the outside of cells, and the three proteins, SecY, SecE and SecG, constituting the main part of the translocation channel through which the secreted proteins pass, as well as SecDF which is a co-factor for the translocation channel, and the like. Inter alia, there have been reports on an expression vector capable of overexpressing secG gene, which encodes SecG protein (Patent Document 2), or a Gram-positive bacterium in which expression of secG gene has been changed by altering the ribosome binding site of SecG gene (Patent Document 3). Thus, it is shown that the breeding of a Bacillus subtilis species having SecG gene destroyed is inhibited during the production of heterologous proteins. It is also reported that in Escherichia coli, variation in secY gene inhibits the breeding at low temperatures or the secretion of proteins (Non-Patent Document 3).
However, a microorganism which overexpresses secY gene, and also has a sporulation-associated gene deleted or inactivated, is not known hitherto.    [Patent Document 1] JP-A-2003-47490    [Patent Document 2] JP-A-2001-510046    [Patent Document 3] US-A-2003/0157642    [Non-Patent Document 1] Nature, 390, 249, 1997    [Non-Patent Document 2] Science, 277, 1453, 1997    [Non-Patent Document 3] Cell, 32, 789, 1983.